A133672 - OEIS

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A133672

a(n) = a(n-1) - 81*a(n-2), a(0)=1, a(1)=9.

1

1, 9, -72, -801, 5031, 69912, -337599, -6000471, 21345048, 507383199, -1221565689, -42319604808, 56627216001, 3484515205449, -1102289290632, -283348020932001, -194062588390809, 22757127107101272, 38476196766756801, -1804851098908446231

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..19.

Index entries for linear recurrences with constant coefficients, signature (1,-81).

FORMULA

G.f.: (1+8*x)/(1-x+81*x^2).

a(n) = Sum_{k=0..n} A133607(n,k)*9^k. - Philippe Deléham, Dec 30 2007

MATHEMATICA

LinearRecurrence[{1, -81}, {1, 9}, 30] (* Harvey P. Dale, Aug 01 2016 *)

CROSSREFS

Sequence in context: A006135 A180836 A218126 * A043079 A367697 A099973

Adjacent sequences: A133669 A133670 A133671 * A133673 A133674 A133675

KEYWORD

easy,sign

AUTHOR

Philippe Deléham, Dec 29 2007

STATUS

approved